B lymphocytes respond to antigen by proliferating and differentiating into antibody-secreting plasmacytes. That response can be enhanced or inhibited by antigen-specific T-helper (TH) or T-suppressor (TS) cells, respectively. The TNP-specific IgA[unreadable]315[unreadable]-secreting MOPC-315 myeloma plasma cells arise by differentiation from malignant small, nonsecretory lymphocytoid stem cells. The proliferation and differentiation of those stem cells can be regulated by distinct subsets of carrier-specific TH and TS cells. I was interested in determining the biochemical changes involved in activation and suppression of MOPC-315 cell secretory differentiation. Until purified helper and suppressor regulatory factors were available from my monoclonal differentiation helper and suppressor T-cell lines, I investigated; (1) whether MOPC-315 differentiation could be modulated by the thymus-independent antigen TNP-LPS (E. coli 055:B5 lipopolysaccharide), and (2) what some of the metabolic requirements were for that modulation. I found that while unconjugated or FITC-conjugated LPS had no effect on 315 cell differentiation when added at doses lower than 10 micrograms/ml in vitro, significant enhancement of 315 cell PFC frequency was observed with from 0.001-0.1 micrograms/ml TNP-LPS and significant inhibition of 315 cell anti-TNP IgA PFC frequency was induced at 1.0 micrograms/ml TNP-LPS. These low dose effects were blocked if monoclonal anti-idiotype[unreadable]315[unreadable] antibody or DNP-glycine were included in the culture media implying that TNP-LPS engagement of surface membrane IgA[unreadable]315[unreadable] was required. The stimulatory dose of TNP-LPS had to be present for only the first 2 hrs to get maximal enhancement measured 48 hrs after culture initiation. The inhibitory dose of TNP-LPS had to be present 24 hrs to get maximal inhibition of PFC frequency and maximal unresponsiveness to helper T-cell stimulation of secretory differentiation. This unresponsiveness once induced lasted 5-7 days. Within the first 1 hr of culture with the stimulatory dose of TNP-LPS, a serine esterase is activated which is required for the PFC frequency enhancement. This serine esterase activity requires phospholipid methylation within the first 15 min of TNP-LPS incubation to be induced. The inhibitory dose of TNP-LPS does not induce these changes but alters the 315 cell metabolism such that subsequent culture with 0.01 micrograms/ml TNP-LPS does not enhance PFC frequency and the serine esterase and phospholipid methylation does not occur. I am continuing these studies and am beginning to determine temporal changes in nuclear, cytoplasmic, and membrane protein phosphorylation using 2D gel electrophoresis. (LB)